Considerable oil reserves around the world are locked in the form of oil sands, also called tar or bitumen sands. Particularly large deposits are known to exist in the Athabasca and Cold Lake regions of Alberta and smaller deposits are found in many areas in the United States including Utah. Oil sands are typically surface mined and the contained bitumen is separated from the sand and recovered using what is commonly referred to as the Clark hot water extraction process. The hot water extraction process is the standard process for recovering bitumen from the sand and other material in which it is bound. The bitumen is then upgraded to obtain a synthetic crude oil.
In the hot water extraction process using existing extraction facilities, tar sand is first conditioned in large conditioning drums or tumblers with the addition of caustic soda (sodium hydroxide) and hot water at a temperature of about 80° Celsius. The nature of these tumblers is well known in the art. The tumblers have means for steam injection and further have retarders, lifters and advancers which create violently turbulent flow and positive physical action to break tip the tar sand and mix the resultant mixture vigorously to condition the tar sands. This causes the bitumen to be aerated and separated to form a froth.
The mixture from the tumblers is screened to separate the larger debris and is passed to a separating cell where settling time is provided to allow the aerated slurry to separate. As the mixture settles, the bitumen froth rises to the surface and the sand particles and sediments fall to the bottom to form a sediment layer. A middle viscous sludge layer, termed middlings, contains dispersed clay particles and some trapped bitumen which is not able to rise due to the viscosity of the sludge. The froth is skimmed off for froth treatment and the sediment layer is passed to a tailings pond. The middlings is often fed to a second stage of froth floatation for further bitumen froth recovery. The water/clay residue from this second stage is combined with the sediment layer from the separating cell for disposal in the tailing ponds.
This conventional hot water technique is energy intensive in part because of the elevated temperature of the initial hot water. Additionally, the process produces an environmental issue in the form of the tailings byproduct which comprises a mixture of water, sand, silt and fine clay particles. Fast-settling sand particles are used to construct mounds, dikes and other stable deposits. However, the leftover muddy liquid, consisting of slow-settling clay particles and water, are the fine tailings and are difficult to dispose of. Fine tailings take a very long time to settle and are produced in significant volumes. Therefore, tailings management is a significant issue that must be addressed by any plant using a hot water bitumen separation process.
Therefore, there is a need in the art for compositions and methods for separating and recovering bitumen from particulate solids which may mitigate the difficulties of the prior art.